Whole grains may benefit a person’s health in a number of ways. For example, by providing a source of fiber and potentially preventing some diseases. However, some people should avoid eating certain whole grains.

Whole grains are cereals and other grains that contain all the natural edible parts of the plant. Compared to refined grains, in which manufacturers have removed some of the nutritional parts.

This article defines whole grains and discusses some of their potential health benefits. It also explores who should avoid eating them.

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The Whole Grain Initiative (WGI) defines whole grains as consisting of the intact, flaked, cracked, ground, or otherwise processed kernel after removing inedible parts, like the husk and hull. The kernel is the seed from which the grain will grow if someone plants it.

Additionally, all the anatomical parts of the grain, including the bran, endosperm, and germ should be present in the same relative proportions as the intact kernel.

The WGI also highlights that when manufacturers label foods as whole grain, they must contain at least 50% whole grain ingredients based on dry weight. Manufacturers that make foods containing 25–50% whole grain ingredients can make a claim on the label to say that the food contains whole grains, but they are not allowed to use the term “whole grain” in the product name.

In the definition of whole grains, the WGI includes cereal grains in the Poaceae grass family and certain pseudocereals. The following are examples of whole grains:

In comparison, manufacturers remove some parts of the grain for taste and appearance to produce refined grains and products, such as white rice and wheat flour.

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The Dietary Guidelines for Americans state that over 90% of females and 97% of males do not consume the recommended intake of dietary fiber. The guidelines suggest that adults eat 14 grams (g) of fiber per 1000 calories to help prevent chronic diseases.

Eating fiber may also help someone feel fuller after a meal and more satisfied, preventing overeating.

Whole grains are a good source of fiber. Research suggests that the amount of total dietary fiber is as follows in certain grains (dry weight):

  • wheat 9–27%
  • oats 10–38%
  • barley 10–30%
  • rice 3–10%
  • buckwheat groats 7–12%

For example, eating a 40 g portion of rolled oats for breakfast contributes just over 4 g of fiber, and two slices of whole wheat bread for lunch adds roughly 3.8 g of fiber. These two items contribute about 28% of the recommended fiber for a daily 2000-calorie diet. People can consume additional fiber from vegetables and fruits.

A 2022 review indicates that eating whole grains may help prevent the development of obesity and metabolic syndrome.

The review suggests that this may be due to the resistant starch content in whole grains, which does not increase blood sugar and may cause a feeling of fullness, or satiety. The large intestine, which is at the end of the digestive tract, digests resistant starch.

A 2022 review of research suggested that eating whole grains may be beneficial for preventing the development CVD.

Studies included in the 2022 review also demonstrated a decreased risk of high blood pressure with increased consumption of dietary fiber.

In addition, whole grains may help manage cholesterol levels in the blood. High cholesterol is a risk factor for CVD.

A 2020 systematic review and meta-analysis found that whole grain intake was associated with a 6–12% lower risk of total cancer mortality when comparing the highest and lowest intake groups. Additionally, eating 15–90 g of whole grains daily was associated with a 3–20% lower cancer risk.

Additionally, the study found that whole grains may help to prevent the following specific types of cancer:

A 2022 review indicated that studies found that consuming dietary fiber from cereals may help manage the blood glucose and insulin response after eating.

Additionally, the review suggested that eating whole grains may help to reduce the risk of developing type 2 diabetes, which occurs as a result of high blood sugar levels rising when the body does not respond to insulin correctly.

People with celiac disease should not eat whole grains that contain gluten. The National Institute of Diabetes and Digestive and Kidney Diseases advises that gluten occurs naturally in some grains, for example:

  • wheat and different types of wheat such as:
    • spelt
    • emmer
    • semolina
    • durum
  • rye
  • triticale, which is a cross between rye and wheat
  • barley and barley extracts

In addition, doctors may advise some people with irritable bowel syndrome (IBS) to avoid grains that contain gluten. However, they may also recommend eating more fiber by including other whole grains, such as rice or buckwheat, in the diet.

A person should speak with a healthcare professional to find out if they may benefit from limiting gluten in their diet.

Whole grains may include a range of cereal grains and some pseudocereals, such as wheat and oats.

In addition to providing a person with dietary fiber, some research suggests that whole grains may help to prevent the risk of certain chronic conditions.

However, people with celiac disease should avoid eating whole grains that contain gluten. Additionally, doctors may advise individuals with IBS to avoid grains containing gluten but increase dietary fiber from other whole grains such as rice.